Data processing system with a touch screen and a digitizing tablet, both integrated in an input device

ABSTRACT

A data processing system includes a multipurpose data input device formed by a touch screen and a digitizing tablet integrated with one another which are activatable independently of each other by proper stimuli. The input device is integrated with a flat panel display in order to establish a visual feedback to the user or to present information pertaining to the entered data after processing. The flat panel display, touch screen and digitizing tablet take a variety of forms and a variety of techniques are utilized to determine which of the touch screen and digitizing tablet is activated at any time.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a data processing system including an inputdevice with a touch screen for inputting data into the system by meansof touch, and a digitizing tablet for inputting data into the system bymeans of manipulation of a stylus near a tablet area, wherein the touchscreen area and the tablet area are at least partly overlapping.

2. Description of the Related Art

Systems employing a touch screen as a data input device are widelyknown. By touching the touch screen at a predetermined position with afinger, or with an object having a similar operation with respect to thetouch screen, data are selected that are indicative of that particularposition. Thereupon the associated data are introduced into the systemand are processed. A touch screen may be combined with a display forselecting data according to the zones shown on the display, such asvirtual buttons. Also, the display may function as a means for providingvisual feedback to the user by showing the information pertaining to thedata after processing. On the basis of the mechanism for activating thetouch screen several types of touch screens can be distinguished. Touchscreens of a first type are those that require for activation an actualcontact between the finger of the user or another object and the screen.An example of such a touch screen employs the localization of theabsorption of surface acoustic waves propagating in a front-panel, theabsorption occurring as consequence of the contact between the panel anda soft tissue such as the user's finger. Another example of a touchscreen of the first type is a screen wherein the reaction-forces andreaction-moments, occurring in the suspension of the screen when it istouched, are registered for deriving the location of the contact.

For touch screens of a second type the presence of an object, such asthe user's finger, in the proximity of the screen is sufficient forenabling the activation of the touch screen without an actual contact.An example of such a touch screen uses a grid of light beams (infrared)in front of and parallel to a front-panel. The presence of an object ata particular location in the grid is detected upon the blocking oflightbeams associated with that particular position. In another exampleof a touch screen of the second type the user's finger in the proximityof the touch screen establishes a capacitive coupling towards ground,which coupling can be detected and localized.

Therefore, the term "touch" in this text will incorporate: "manipulatingan object in the detection range of", in addition to: "establishing anactual contact with".

It is a disadvantage of the conventional systems that these are notsuitable for both a data-input by means of touching the touch screen atpredetermined zones, like virtual buttons, with a finger or a similarobject suitable for pointing, and a data-input by means of writing,drawing or accurate pointing on the screen with a suitable stylus. Inother words, the touch screens of the known systems cannot represent avirtual control panel with buttons, or a keyboard as well as adigitizing tablet.

Writing or drawing in an ergonomically justified way implies that thewriter's or drawer's hand is supported by a surface more or lesscoinciding with the area to be written upon. The known touch screensrequiring an actual contact for activation will register simultaneouslythe contact of the stylus with the screen and the contact of thewriter's hand with the screen without discriminating between the twoimpressions. The known touch screens that are activatable bymanipulating an object, like the user's finger, in front of the screencannot discriminate between the stylus and the user's hand either. Forexample, both the hand and the stylus intercept the light beams of thegrid that couples a plurality of light transmitters with a plurality ofassociated light detectors, or both enable a capacitive coupling towardsground.

Also the touch screen and the digitizing tablet operate with mutuallydifferent resolutions on stimuli, since the accuracy of a touch dependson the dimensions of a finger (order of magnitude: 1 cm) and theaccuracy of a data entry with a stylus depends on the dimensions of thecooperative part of the stylus (order: 1 mm or even smaller).

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a data processingsystem with a compact data input device enabling the entering of datainto the system by touching the touch screen with a finger or the likeas well as by writing, drawing or accurate pointing on the screen bymeans of an appropriate stylus as desired.

A data processing system according to the invention is thereforecharacterized in that the touch screen comprises a first sensing meansfor converting a first stimulus representative of a touch presence andlocation into a first signal for the data handling means, and that thedigitizing tablet comprises a second sensing means for converting asecond stimulus representative of a presence and location of the stylysinto a second signal, the first and second sensors being physicallydistinct and their output signals being fed out in parallel.

Physically distinct sensing means, that is, two separate conversionmechanisms, where components involved in converting a stimulus into asignal are allocated to either the first or the second sensor, have theadvantage that they are easier to manufacture, because the two distinctsensing devices can be manufactured separately and added successively tothe system. It is also convenient in use, because the output signals canbe fed out in parallel leaving the data handling means the option tohandle the outputs in parallel or one by one. Thus, the two sensingmeans will not interfere with one another and do not need to contend forshared sensing means, which allows for simplicity and flexibility in thedesign of application programs utilizing such a combined touch screenand tablet.

A compact input device is realized by integrating a touch screen and adigitizing tablet with one another. As both are activatableindependently of one another, the touch screen will only respond to atouch and the digitizing tablet will only respond to the stylus. Thetouch screen and the digitizing tablet are integrated on the organizinglevel, that is employing a data handling means that is common to both.The data handling means handles the data originating in the touch screenas well as the data originating in the digitizing tablet.

Several types of separate digitizing tablets are known. In a firstexample, the stylus radiates ultrasonic waves. For instance by means ofat least two receivers a cross-bearing then indicates the momentaryposition of the stylus. In a second example, the stylus emitselectromagnetic waves that induce currents in two sets of oblongconductors that lie in mutually different orientations in two parallelplanes. The inductive currents in the pair of crossing conductors thatoverlap the area of the momentary position of the stylus are detectedfor localization of the stylus. In a third example, the digitizingtablet comprises a conductive sheet that conducts alternating currentsin such a way, that the phase or amplitude of the resultingelectromagnetic field, measured at a predetermined location of thesheet, is indicative of said location. Via a capactive coupling thestylus detects the associated electromagnetic field exhibiting theparticular phase or amplitude. The information contained by the phase oramplitude can then be transmitted to the system and thereupon beprocessed as an indication of the stylus' momentary position. In a fifthexample the digitizing tablet comprises a resistive sheet wherein theradiating stylus induces currents. By measuring the aggregated currentsin two anti-parallel directions a quantity can be derived indicative ofthe aggregated resistance that the currents have overcome. The ratio ofthe resistances that correspond to the aggregated currents in twoanti-parallel directions is associated with the ratio of distances thecurrents have had to travel through the sheet. By deriving these ratiosfor two mutually independent directions the area can be located at whichthe currents originated, that is the area in the nearest proximity ofthe radiating stylus.

At this point it will be clear for the man skilled in the art that aplurality of combinations of touch screen and digitizing tablet bothintegrated within the same compact input device will be possible,dependent on the screen's and the tablet's activation mechanisms oraccessability in view of their position relative to each other.

Several combinations are possible. The touch screen and the digitizingtable can be integrated contiguously within substantially the same areaof the front panel of the input device. This set up enables acooperation between the touch screen and the digitizing tablet, thetouch screen functioning for example as an input device for selecting aparticular operating mode by means of soft keys of the digitizing tabletas a data-receiver. The touch screen and the digitizing tablet need notbe coplanar. For instance, the touch screen part may be integrated in araised border of the input device under a substantial angle with theplane digitizing tablet for ergonomic reasons. Also the touch screen andthe digitizing tablet may occupy areas of substantially differentproportions. In another embodiment the touch screen and the digitizingtablet are stacked permitting the input device to have limiteddimensions. Again, the touch screen and the digitizing tablet may occupyareas of substantially different proportions. Preferably, a selectionmeans, like a toggle switch, is provided for alternatingly turning on oroff either part of the input device in order to prevent an unintentionaldata entry form occurring, for example from a hand resting on the inputsurface while it manipulates the stylys. As an alternative, such anundesired touch signal can be avoided by using a data processing systemcomprising touch disabling means for disabling touch location sensing inresponse to stylus presence detection.

Preferably, the structure containing the touch screen and the digitizingtablet itself is integrated with a display for the visual feedbacktowards the user. In view of the dimensions of this laminatedcomposition the display preferably is of the so-called flat panel type.

Within the technical field of the flat panel displays, one candifferentiate between self-emitting (or active) panels andnon-self-emitting (or passive) panels. An example of an active panel isa thin film electro-luminescent display (ELD). Such a display comprisesa matrix of capacitors, each whereof has a dielectric layer between twoelectrodes. With a sufficiently high, alternating electrical fieldacross the dielectric layer, containing for instance ZnS and Mn,hole-electron pairs will be generated that will cause the radiation uponrecombination.

Another example of an active flat panel display is a plasma displaypanel (PDP) based on localized vapour discharge.

An example of a passive flat panel display is a liquid crystal display(LCD). In a LCD the polarization of light by liquid crystals can bevaried under control of an electric field, giving rise to the modulationof the amount of light transmitted when appropriate polarizers are used.In view of the relatively low power dissipation and of the relativelylow cost price, the LCD prevails over the other types. LCD's suitablefor integration with the touch screen and the digitizing tablet may bethe Twisted Nematic LCD's, with an active matrix with a switchingelement (e.g. a transistor or a diode-ring) for each pixel, the SuperTwisted Nematic LCD's without an active matrix, or a Ferro-Electric LCDcomprising a memory inherent in the display itself.

Preferably, the data processing system according to the inventioncomprises mouse means coupled to the input device in order to enable allcurrent ways of data entry. For instance, the "mouse" is operated viathe touch screen by indirect pointing, that is by touching with a fingera particular sector of a segmented compass-card that is shown on thetouch screen resulting in relative displacements of the cursor, or viathe digitizing tablet by direct pointing and cursor-control fordragging. Thus, the invention provides a data processing system that iscompact, portable, and multi-functional with respect to data entry.Also, within this context reference is made to Dutch Patent Application8901805 of the same Applicant wherein means are disclosed for convertinga touch screen into a keyboard which permits professionaly highdata-entry speed by way of a tactile feedback towards the user.

Preferably, in case at least the touch screen or the digitizing tabletis activatable in an electrical way, the input device comprises aconductive sheet at a fixed potential for protecting the touch screen orthe digitizing tablet against electromagnetic radiation originating inthe control circuitry of the data processing system, for instance due tothe control of the display. In a stacked embodiment there may beprovided a transparent conductive layer between the digitizing table andthe touch screen on the one hand and the radiating circuitry part of thedisplay on the other hand.

As has been stated previously, it will be clear to the man skilled inthe art what kind of touch screen digitizing tablet and, display can beintegrated within a single panel. The usefulness of a particularcombination will depend among others on the activation mechanisms of thetouch screen and of the digitizing tablet, the possibility of realizingtransparent embodiments of said latter parts, and the insusceptibilityof the various parts constituting the panel to each other's operation.

BRIEF DESCRIPTION OF THE DRAWING

Various embodiments of an input device comprising particularcombinations of a touch screen, a digitizing tablet and a flat paneldisplay for use in a data processing system according to the inventionwill be illustrated by way of non-limitative examples with reference todrawing, wherein:

FIG. 1 is an exploded isometric view of a first diagrammatic example ofan input device containing as integral parts thereof: a touch screenbased on the use of surface acoustic waves, a digitizing tablet based ona capacitive coupling between the tablet and an appropriate stylus, anda LCD, as a display;

FIG. 2 is an exploded isometric view of a second diagrammatic examplecontaining a touch screen and a display as in FIG. 1 and using adigitizing tablet based on an inductive coupling between the tablet andan appropriate stylus;

FIG. 3 is an isometric view of a third diagrammatic example using atouch screen and a display as in FIG. 1 and comprising a digitizingtablet based on localizing the position of an appropriate stylus by across-bearing of ultrasonic waves;

FIG. 4 is an isometric view of a fourth diagrammatic example employing atouch screen, that registers the forces and movements in the suspensionof the screen for determining a place of contact, and a digitizingtablet integrated on a surface of a LCD, the tablet's operation beingbased on ultrasonic-wave-cross-bearing;

FIG. 5 is an isometric view of a fifth diagrammatic example of an inputdevice employing a touch screen and a digitizing tablet, both based on acapacitive coupling with the input device, while using a force-thresholdfor determining the activation of the touch screen; and

FIG. 6 is an isometric view of a sixth diagrammatic example of an inputdevice wherein the display is sandwiched between the touch screen andthe digitizing tablet, and

FIG. 7 is a generalized schematic diagram of a data processing system inaccordance with the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIG. 7, the data processing system 200 of the presentinvention is seen to generally comprise a touch screen 10 for receivinga touch as by a user's finger 34, a digitizing tablet for interactingwith a stylus 68 proximate thereto, first sensing means 202 for sensingthe presence and location of the touch within the area of touch screen10, and second sensing means for sensing the presence of stylus 68 abovedigitizing tablet 68 and its location within the tablet's area. Thefirst and second sensing means generate respective signals 206, 208 andfeed them in parallel to data handling means 210.

Throughout the Figures same reference numerals with designate identicalor corresponding parts.

In FIG. 1 there is shown a first diagrammatic example of an input devicefor use in a data processing system according to the invention. Theinput device comprises a layered structure with the touch screen 10 atthe top, the digitizing tablet 12 in the middle and a liquid crystaldisplay (LCD) 14 at the bottom. For clarity the components constitutingthe layered structure have been drawn spaced out. In practice, thestructure is a compact laminated device. The touch screen 10 operates onthe basis of surface acoustic waves (SAW), radiated by transmitters 16and 18 into the front panel 20 along respective series of reflectiveelements 22 and 24 in order to spread the transmitted waves across thepanel 20. The panel is further provided with receivers 26 and 28 thatreceive the waves after they have been reflected by respective otherseries of reflective elements 30 and 32. A SAW-pulse transmitted bytransmitters 16 or 18 will be received retarded and broadened byreceivers 26 or 28. In case a soft tissue, like the user's finger 34,contacts the panel 20, some of the energy of the SAW-pulse will beabsorbed by the tissue, resulting in a decreased amplitude of the pulsecomponents 36 and 38 passing through the location of contact 40. Themoment of the receipt of said reduced components, related to the momentof transmission, is indicative of the momentary position 40 at which theabsorption occurs. In order to avoid mutual interference, transmitters16 and 18 may alternate transmission.

The digitizing tablet 12 is situated below touch screen 10. The tablet12 comprises an electrically resistive homogeneous sheet 42 of atransparant, electrically conductive substance, for instanceIndium-Tin-oxide. Along its circumference sheet 42 is provided with aplurality of series of highly conductive, uniformly distributedelectrodes 44, 46, 48 and 50 for establishing electrical contacts withthe resistive sheet 42. Each series of electrodes is connectable to ordisconnectable from an associated conductor 52, 54, 56 and 58, by meansof an associated series of switches 60, 62, 64 and 66. The switches 60and 64 are operated simultaneously. Also the switches 62 and 66 areoperated simultaneously. The pairs of switches 60/64 and 62/66 areconnected alternately with their associated conductors 52/56 and 54/58,respectively. This basic arrangement may be used in various ways.

In a first appliance the stylus 68 may comprise a source for generatingelectromagnetic radiation that couples capacitively with sheet 42 and anarea 70 through panel 20 for thereupon inducing currents in sheet 42.These currents will spread over sheet 42 and will be gathered byconductors 52/56 or 54/58 at zero potential, that have been connected tosheet 42. Now, the current in each conductor is indicative of theaggregated resistance between area 70 and the relevant conductor. Sincethe sheet is homogeneous, this aggregated resistance is a quantity thatcorresponds with a respective distance between an area 70 and therespective conductor. Therefore, by sensing the aggregated currents inboth pairs of conductors connected to sheet 42 the area 70 can beaccorded coordinates that correspond to the stylus' 68 momentarilyposition. For sensing the aggregated currents each conductor that isconnected to sheet 42 is coupled with a detector (not shown) which maycontain: a current-to-voltage converter operating at zero potential("virtual ground"), an amplifier, an ac-to-dc converter, ananalog-to-digital converter and a microcontroller with appropriatesoftware for calculating the coordinates and for possibly adjusting forany deviation between calculated coordinates and physical position ofthe stylus 68 due to the particular embodiment of the shown inputdevice.

In a second appliance a time-varying electromagnetic field isestablished across sheet 42 which field has a local phase that isindicative of a position within the field. To this end conductors 54 and58 may supply synchronously varying simple harmonic voltages to sheet42, which voltages have a predetermined mutual phase difference, likefor instance a sine and a cosine time-dependence. By first sensing thephase by a probe (not shown) in stylus 68 while conductors 54 and 58 areactive, and then sensing the phase by the probe in stylus 68 whenconductors 52 and 56 carry the time-dependent voltages, the location ofthe stylus can be derived from the registered phases.

The digitizing tablet 12 is disposed on top of a flat panel display 14of the LCD type. As both the touch screen 10 and the digitizing tablet12 are transparant the display 14 can be viewed through these devices,for instance in order to provide visual feedback to the user whilewriting or drafting with stylus 68 within the range of digitizing tablet12 or in order to select data to be processed on the basis ofinformation shown on LCD 14 by touching touch screen 10 at apredetermined position associated with said data.

As has been stated above the figure presents an exploded view of a datainput device for use in a data processing system according to theinvention. The layered structure may in practice be realized as a verycompact device, for instance by using the upper surface of a same panel20 for depositing a pattern thereupon constituting the reflectiveelements 22, 23, 38 and 32, and by using the downfacing surface fordepositing thereupon a layer of resistive material constituting sheet 42preferably of Indium-Tin-oxide for its transparancy. In anotherembodiment the features constituting the reflective elements 22, 24, 30and 32 and the sheet 42 may be integrated within one of the polarizers140 of a LCD, the reflective elements at the one surface foraccessability, the resistive sheet 42 at the other surface of therespective polarizer. In a further embodiment the digitizing tablet 12and the touch screen 10 each may comprise a separate associated panellike panel 20 in view of convenient manufacturing said devices.

Since both the touch screen 10 and the digitizing table 12 utilizedifferent activation mechanisms, (the touch screen 10 is activatedmechanically, the digitizing tablet 12 is activated electrically) theinput data transferred into the data processing system via the inputdevice shown in FIG. 1 are distinguishable. In order to feed input dataselectively into the data processing system, the system may be providedwith a selection-switch to enable either the touch screen 10 or thedigitizing tablet 12. In the alternative, stylus 68 may incorporateeither a (piezo-ceramic) pressure sensor with appropriate processing orsimply a pressure-sensitive switch for turning-off the touch screen 10and turning on the digitizing tablet 12 upon contacting the surface ofthe input device.

In FIG. 2 a second example is shown of a disassembled input device foruse in a data processing system according to the invention. The examplein this FIG. 2 discloses the LCD 14 to have a polarizer 140 forming anisolating panel as a part of the digitizing tablet 12. The digitizingtablet comprises two sets of oblong conductive loops that lie in amutually perpendicular orientation in two parallel planes separated byan electrically isolating polarizer 140. For clarity only two crossingloops 80 and 82 have been drawn. By manipulating a stylus 68 having atip 84 that radiates electromagnetic waves inductive currents occur inthe loops 80 and 82 that overlap the projection onto the digitizingtablet 12 of an area 86 at the surface of the input device, in whicharea 86 the stylus tip 84 is maintained.

By sensing those inductive currents the momentary location of thestylus' tip 84 is determined. Preferably the stylus is provided with apressure sensitive switch at tip 84 for radiating only when contactingthe surface of the input device upon sensing a pressure exceeding apredetermined threshold. Preferably, the conductive loops are made of atransparent material, for instance Indium-Tin-Oxide. As in FIG. 1 inputdata are discriminated on the basis of the different physical charactersof the stimuli, the touch screen 10 being susceptible to mechanicallydraining the energy of the surface acoustic waves, the digitizing tabletbeing activated electrically by inducing currents in sets of crossingloops.

In FIG. 3 a third example is shown of an input device for use in a dataprocessing system according to the invention. The digitizing tablet 12and the touch screen 10 now both have been integrated on one of thepolarizers 140 of LCD 14. The touch screen 10 is of thesurface-acoustic-wave type already described with reference to FIG. 1.At the same surface the digitizing tablet 12 is realized, the operationthereof being based upon ultrasonic waves propagating across thepolarizer in the air. The surface is provided with two ultrasonicreceivers 90 and 92 for determining the position of a source ofultrasonic pulses at the tip 74 of stylus 68, for instance by means ofcross-bearing. Preferably, more than two ultrasonic receivers areemployed in order to ensure that position decoding is always possible inspite of the presence of the user's hand that may obstruct theultrasonic waves.

FIG. 4 discloses an input device wherein the operation of the touchscreen part 10 employs the registering of the reaction forces and-moments in the suspension of the device and wherein the digitizingtablet 12 uses the capacitive coupling between the tablet and a specialstylus as has been described previously with reference to FIG. 1. Thetouch screen part is established by suspending the LCD 14 by fourelastic devices 104, 106, 108 and 110, that are attached to a rigidframe 112. Each elastic device comprises a strain gauge, for instance apiezo resistive strain gauge printed on an aluminum substrate, likegauges 114, 116, 118 and 120. Each gauge incorporates severalresistances that, for example, are connected in Wheatstone bridgeconfigurations (not shown) in order to derive from the variousreaction-forces and -movements in the suspension, occurring when anexternal force is applied to the upper surface of the input device, thelocation whereto the external force is applied.

Filter means may be provided for filtering out reaction forces andmoments, that are due to the input device's inertia when it is moved andtherefore bear no relation with any intended activation. For instance,the filter means may be realized in software for discriminating signalsthat have predetermined characteristics representing an intendedactivation by touching the input device with a finger or a stylus in aspecified, ergonomical way.

The use of the gauges may be restricted to measure the force in order tocompare it with a threshold for ergonomic reasons. This will beclarified by way of FIG. 5, which is similar to the previous FIG. 4 to alarge extent. Now, the homogeneous electrically resistive sheet 10 and12 plays a part in both the digitizing tablet 12 and the touch screen10. In order to function as a touch screen for being activated by theproximity of finger 130 appropriate electronic circuitry (not shown) isprovided for detecting a capacitive coupling from sheet 10 and 12towards earth via finger 130 and for thereupon deriving the finger's 130position. This item is well known in the art. In order to function as adigitizing tablet cooperating with stylus 68 other appropriateelectronic circuitry (not shown) is incorporated for determining thestylus' 68 momentary position in the way as has already been describedwith reference to FIG. 1. In this particular embodiment the stimuli thatrepresent the finger's 130 touch or the presence of stylus 68 foractivating the touch screen part or the digitizing table part,respectively, are of a same physical character (a signal detectedcapacitively).

The aggregated force measured by the gauges 114, 116, 118 and 120 iscompared with a threshold by a comparator (not shown) for determiningwhen the touch screen should be activated. Preferably, the thresholdcorresponds with a force of 60-80 gram associated with the pressing of akey in a conventional alfa-numerical keyboard of a typewriter. Only whenthe applied force exceeds the predetermined threshold the touch screenwill be activated. Therefore, the use of gauges makes an adjustment ofthe touch screen part possible with respect to the required force to beapplied for activating the touch screen.

Within this context it should be mentioned that the use of gauges as atouch-force thresholding means may be of particular advantage forergonomic reasons in respect of a tactile feedback when employing atouch screen of the kind, that does not require an actual contact foractivation, for instance the capacitive touch screen discussed above andthe touch screen based on obstructing light beams that form a grid infront of a front panel.

In all examples given thus far, the digitizing tablet part had to betransparent because of its location in front of the display. An examplewherein the transparancy of the tablet is irrelevant is shown in FIG. 6.

In FIG. 6 an input device according to the invention is disclosed thatis comparable with the one presented in FIG. 2 except for the mutualrelative positions of the various parts and the compactness of thedevice. The touch screen part 10 is integrated on the upper surface ofpolarizer 140 of LCD 14 as has been described with reference to FIG. 3.The digitizing tablet part 12 has been realized with non-transparentconductors 80, 82 on a non-transparent sheet 152. This structure can beemployed when the display 14 is passive (requiring no additionalback-lighting), reflective and (preferably) thin. The loops 80 and 82now can be made of for instance Cu or Ag. The specific conductivity ofthese materials is higher than that of Indium-Tin-Oxide and consequentlygives rise to a higher sensitivity and accuracy of the digitizingtablet.

I claim:
 1. Data processing system comprising an input device with atouch screen for inputting data into the system by activating anoperative touch screen area thereof by a first stimulus comprising apresence and location of a touch, the input device also comprising adigitizing tablet for unpitying data into the system by activating thetablet by a second stimulus comprising a presence and location of astylus near an operative tablet area thereof, the touch screen area andthe tablet area at least partially overlapping, the touch screen and thedigitizing tablet being coupled to a data handling means for processingthe data, wherein the touch screen comprises a first sensing means forconverting said first stimulus into a first signal feeding the datahandling means, said first sensing means comprising all components ofsaid input device involved in converting said first stimulus into saidfirst signal, and wherein the digitizing tablet comprises a secondsensing means for converting said second stimulus into a second signalfeeding the data handling means in parallel with said first signal, saidsecond sensing means comprising all components of said input deviceinvolved in converting said second stimulus into said second signal, thefirst and second sensing means being physically distinct from each otherby sharing no component of said input device involved in converting therespective first and second stimuli to the respective first and secondsignals.
 2. Data processing system as claimed in claim 1, wherein thetouch screen and the digitizing tablet are stacked in the input device.3. Data processing system as claimed in claim 1, wherein at least thetouch screen or the digitizing tablet can be disabled by means of aswitch.
 4. Data processing system as claimed in claim 1, comprisingtouch disabling means for disabling touch location sensing in responseto stylus presence detection.
 5. Data processing system as claimed inclaim 1, wherein the touch screen and the digitizing tablet areintegrated with a data display means.
 6. Data processing system asclaimed in claim 5, wherein the data display means comprises a liquidcrystal display, a polarizer whereof being integrated with at least thetouch screen or the digitizing tablet.
 7. Data processing system asclaimed in claim 1, wherein the touch screen comprises:a surface beingprovided with source means for transmitting surface accoustic wavesacross the surface and being provided with receiver means for receivingthe surface accoustic waves; a processing means coupled to the receivermeans for on the basis of an absorption of the surface accoustic wavesat the surface determining a location of the absorption.
 8. Dataprocessing system as claimed in claim 1, wherein the touch screencomprises:a resistive layer; means for determining a location of acapacitive coupling between the resistive layer and earth via the user.9. Data processing system as claimed in claim 1, wherein the touchscreen comprises:a rigid surface coupled to a rigid frame by means ofstress or strain sensitive elements; means for upon monitoring thestress or strain in the elements determining if and where an externalforce is applied to the rigid surface.
 10. Data processing system asclaimed in claim 9, wherein filter means are provided for discriminatingthe stress or strain that is due to the intended activation of the inputdevice by the user as contrasted with the stress or strain due to theinput device's inertia when it is moved.
 11. Data processing system asclaimed in claim 1, wherein the touch screen comprises:grid means forgenerating a grid of light beams in front of and in parallel to a frontpanel of the input device; detection means for upon detecting anobstruction of at least one light beam processing data associated withthe particular beam as an indication of a position of the obstructionrelative to the input device.
 12. Data processing system as claimed inclaim 1, wherein the digitizing tablet comprises: means for determininga location of the stylus with respect to the input device by means of anultrasonic coupling between the digitizing tablet and the stylus. 13.Data processing system as claimed in claim 1, wherein the digitizingtablet comprises:a resistive layer; means for establishing atime-dependent electromagnetic field across the resistive layer whichelectromagnetic field has a phase or amplitude that is dependent on aposition in the field, the stylus being provided with a detectorsensitive to the electromagnetic field; processing means coupled to saiddetector for upon sensing the electromagnetic field determining alocation of the stylus with respect to the input device.
 14. Dataprocessing system as claimed in claim 1, wherein the digitizing tabletcomprises:a resistive layer, the stylus being provided with source meansfor inducing currents in the resistive layer; sensing means for sensingaggregated currents flowing in two antiparallel directions across theresistive layer; processing means coupled with the sensing means or uponsensing the aggregated currents determining a location of the styluswith respect to the input device.
 15. Data processing system as claimedin claim 1, wherein the digitizing tablet comprises:a first layercomprising a first set of conductive conductors in a first orientation;a second layer parallel to the first layer, comprising a second set ofconductive conductors in a second orientation electrically isolated fromthe first set, the stylus being provided with source means forgenerating inductive currents in said sets of conductors; sensing meansfor sensing the inductive currents; processing means coupled to saidsensing means for sensing the inductive currents determining a locationof the stylus with respect to the input device.
 16. Data processingsystem as claimed in claim 15, wherein the touch screen and thedigitizing tablet are integrated with a data display means comprising aliquid crystal display, a polarizer thereof being disposed between thefirst and the second layer.
 17. Data processing system as claimed inclaim 13, wherein the touch screen and the digitizing tablet areintegrated with a data display means comprising a passive, reflectiveliquid crystal display, the digitizing tablet being disposed underneathan active portion of the liquid crystal display.
 18. Data processingsystem as claimed in claim 1, the input device being suspended by meansof stress or strain sensitive elements for detecting an external forceapplied to the input device, comparator means being provided forcomparing the applied force with a predetermined threshold, for in caseof exceeding the threshold activating the input device.
 19. Dataprocessing system as claimed in claim 1, wherein the stylus incorporatesa pressure sensor for enabling a cooperation between the stylus and theinput device upon the sensor sensing a pressure exceeding apredetermined threshold.
 20. Data processing system as claimed in claim1, wherein at least the touch screen or the digitizing tablet iselectrically activatable, there being provided a conductive sheet at apredetermined potential for protecting the touch screen or thedigitizing tablet against electromagnetic radiation originating incontrol circuitry of the data processing system.
 21. Data processingsystem as claimed in claim 5, characterized in that the data processingsystem is provided with mouse means for displaying a cursor to beoperated via at least the touch screen or the digitizing tablet eitherby pointing to and pressing on a relevant location for repositioning thecursor or by pointing to a segmented compass-card with virtual"click"-buttons, a segment of the compass-card being indicative of adirection of movement of the cursor upon activation of the segment. 22.Data processing system as claimed in claim 2, wherein the touch screenand the digitizing tablet are integrated with a data display means. 23.Data processing system as claimed in claim 22, wherein the data displaymeans comprises a liquid crystal display, a polarizer whereof beingintegrated with at least the touch screen or the digitizing tablet.